Flexography

Flexography (also called surface printing), often abbreviated to flexo, is a method of printing most commonly used for packaging (labels, tape, bags, boxes, banners, etc.).

A flexographic print is made by creating a positive mirrored master of the required image as a 3D relief in a rubber or polymer material. A measured amount of ink is deposited upon the surface of the printing plate (or printing cylinder) using an engraved anilox roll whose texture holds a specific amount of ink. The print surface then rotates, contacting the print material which transfers the ink.

One method of plate development uses light-sensitive polymer. A film negative is placed over the plate, which is exposed to ultra-violet light. The polymer hardens where light passes through the film. The remaining polymer has the consistency of chewed gum. It is washed away in a tank of either water or solvent. Brushes scrub the plate to facilitate the "washout" process. This method is considered "old-fashioned," but is still widely used in smaller operations, and is still taught in most high school and college flexo programs.

Originally flexographic printing was basic in quality. Labels requiring high quality have generally been printed using the offset process until recently. In the last few years great advances have been made to the quality of flexographic printing presses.

The greatest advances in flexographic printing have been in the area of photopolymer printing plates, including improvements to the plate material and the method of plate creation, usually photographic exposure followed by chemical etching, though also by direct laser engraving.

Digital direct to plate systems have dominated the industry recently with their better resolution and the ability to print four color process (or more) as well as offset. Companies like Dupont, MacDermid, Kodak and Esko have pioneered the latest technologies with advances in FAST washout and the latest screening technology, even companies who make plates in house are going to trade shops to get these high quality plates.

Laser-etched anilox rolls also play a part in the improvement of print quality. Full color picture printing is now possible, and some of the finer presses available today, in combination with a skilled operator, allow quality that rivals the lithographic process. One ongoing improvement has been the increasing ability to reproduce highlight tonal values, thereby providing a workaround for the very high dot gain associated with flexographic printing.

Flexo has an advantage over lithography in that it can use a wider range of inks, water based rather than oil based inks, and is good at printing on a variety of different materials. Flexographic inks, like those used in gravure and unlike those used in lithography, generally have a low viscosity. This enables faster drying and, as a result, faster production, which results in lower costs.

Printing press speeds of up to 600 meters per minute (2000 feet per minute) are achieveable now with modern technology high-end printers, like Flexotecnica [http://www.cerutti.it/group/flexotecnica/company.html] , which introduced the world's first 12-color central impression (CI) drum press at Drupa 2008. Other press formats, such as in-line and stack presses, are available from Tresu and other suppliers.

History

Flexography was created in 1873 by Peter Belanger, a Canadian school teacher. He is often credited with creating the Anilox Roll. Many refer to Belanger as "The Jesus Of Flexography" due to his abundant flowing hair that is comparable to that of Jesus Christ. Born in 1836, to James and Harriet Belanger, Peter found himself interested in printing, when his father took him to see the regional printing press when Peter was only 5 years old. Belanger, also an excellent graphic designer (at the time), was the first and only winner of the Nobel Printing Prize, in 1901. Due to its lack of importance, the award was removed from the Nobel series of awards along with the Athletics and Journeyman awards.

His first, and most famous invention was the "Flexographic Printing Machine", which spooled paper and ran it through a printing press. He soon realized his plans were flawed due to many mis-prints. The ink was not coming out at appropriate intervals for the speed of the paper spool. He then created the Anilox Roll.

After inventing the Anilox roll in late 1873, Belanger started teachers college at the University of Toronto. He graduated after 3 years of studying, and became a school teacher, teaching his students the importance of flexography in the business world. A small side project of his teachings, was his communication technology course, offered outside of his institution. This was a very controversial course however, as many of his students claimed that his communication technology course was used as a way to advertise his flexography courses at his institution.

Belanger was rumored to have stolen the original plans for the "Flexographic Printing Machine" from Kelly Fotinos, a renowned Canadian social scientist. The process of flexography was then dubbed “aniline printing,” named for the aniline oil used in the ink, that would be jetted out by the use of Anliox roll. In 1890, the first patented press was built in England by Bibby, Baron and Sons, using many of Belanger's ideas. The water-based ink smeared easily, leading the device to be known as “Bibby’s Folly”.In the early 1900’s, other European presses were developed using rubber printing plates. But by the 1920s, most presses were made in Germany, where theprocess was called “gummidruck”.

During the early part of the 20th century, the technique was used extensively in food packaging in the United States. However, in the 1940’s, the Food and Drug Administration classified aniline dyes as unsuitable for food packaging.Printing sales plummeted. Individual firms tried using new names for the process, such as “Lustro Printing” and “Transglo Printing,” but met with limited success. Even after the government approvedthe aniline process, sales continued to decline. Intent on re-popularizing aniline printing by changing its name, Franklin Moss, president of Mosstype Corporation, surveyed the industry in 1951 and received over 200 different name suggestions. In October of 1952, thenew name was announced; “flexography.” [The Pressman]

Products

Typical products printed using flexography include brown corrugated boxes, flexible packaging including retail and shopping bags, food and hygiene bags and sacks, flexible plastics, self adhesive labels, and wallpaper. A number of newspapers now eschew the more common offset lithography process in favour of flexo.

In education

The Flexo in Education Program, formerly The Flexo in High School Program, was started at South Mecklenburg High School in Charlotte, North Carolina by the Flexographic Technical Association in 1993. Since its inception many other high school programs have been started. For example Asheville High School in Asheville, NC, The Applied Technology Center in Rock Hill, SC, Fort Mill High School in Fort Mill, SC, and others. The program has even gone international with the inclusion of Gordon Graydon Memorial Secondary School in Mississauga, Ontario, Canada. The program was re-named to become The Flexo in Education Program because post-secondary institutions began to participate in the program. Many technical colleges and universities incorporate flexography into their curriculum. For example [http://www.fvtc.edu/graphicarts Fox Valley Technical College Flexographic Research and Training Center in Appleton WI] [http://graphics.clemson.edu The Department of Graphic Communications] and [http://www.clemson.edu/centers-institutes/printcon the Clemson University Printing and Converting Research Center] at [http://www.clemson.edu Clemson University] , [http://www.cpcc.edu Central Piedmont Community College] , [http://www.chowan.edu Chowan University] , [http://www.appstate.edu Appalachian State University] , the Graphic Communications Management program at Ryerson University, and others include flexography in their curriculum.

Sadly, Charlotte-Mecklenburg Schools, the school district where Flexo in Education got its start, announced in 2008 that the first ever Flexo in High School program at South Mecklenburg High School would be discontinued. The building where their flexography lab was located was demolished Monday, July 7, 2008, to make way for a new 3-story building to house the school's science and technology department. The school district determined that it would be too difficult and expensive to move, store, and re-install press and equipment in the old lab. It was, instead, donated to another school in North Carolina to start a new flexo program.

Flexographic printing inks

The nature and demands of the printing process and the application of the printedproduct determine the fundamental properties required of flexographic inks.Measuring the physical properties of inks and understanding how these areaffected by the choice of ingredients is a large part of ink technology. Formulationof inks requires a detailed knowledge of the physical and chemical properties ofthe raw materials composing the inks, and how these ingredients affect or reactwith each other as well as with the environment. Flexographic printing inks areprimarily formulated to remain compatible with the wide variety of substrates usedin the process. Each formulation component individually fulfils a special functionand the proportion and composition will vary according to the substrate.

References

1.http://www.thepressman.com/Pressman%20April%202003.pdf